In recent years, storage devices comprising nonvolatile memories have been widely prevalent. As such a storage device, a solid state drive (SSD) based on a NAND flash technology is known. The storage device used in a computing system such as a server of a data center is required to exert high-level I/O performance. For this reason, a new interface between a host side and a storage device side has been recently proposed.
However, if the number of defective blocks included in the nonvolatile memory is increased, increase in the amount of replacement information to replace the defective blocks with the other blocks and increase in the read latency time which results from this replacement processing may occur. This may be a factor which degrades the I/O performance of the entire system.